Mr. Buackwatt on the Pulvilli of Insects. 491 
asserts, though when placed in such a situation relative to the 
eye of the observer that the hairs connected with them are fore- 
shortened, they certainly present an appearance which, on a 
superficial view, might lead to the latter conclusion. If the 
slender bristles on the inferior surface of the pulvilli of some of 
the larger Coleoptera, Prionus cervicornis for example, be very 
highly magnified, each, beside the numerous short hairs which 
project from its sides, will be found to have a small dense brush 
of exceedingly minute hairs at its extremity; and as the hairs 
on the pulvilli of flies, and many other insects belonging to 
various orders and genera, with which I have experimented, 
perform a function similar to that exercised by the bristles, and 
also exhibit a striking resemblance to them in external appear- 
ance, it is extremely probable that they are analogous in struc- 
ture; though from the smallness of their dimensions, I have not 
yet been able to satisfy myself that this is the case by direct 
observation, notwithstanding I have employed the highest mag- 
nifying power at my command. The hold which insects are 
enabled to take of any roughness or irregularity of surface by 
means of the fine hairs composing the brushes must be very 
considerable; and whoever examines the most carefully polished 
glass in a favourable light with a powerful lens, will speedily be 
convinced that it is not free from flaws and imperfections. 
That some species of spiders can support themselves against 
gravity on the sides of polished bodies by the assistance of a 
mechanical apparatus similar in principle to that employed by 
insects in like circumstances, I have announced in a communi- 
cation recently made to the Linnean Society *; and the fact 
affords a strong collateral proof of the truth of my theory. 
I am aware that the males of several aquatic beetles have the 
tarsi of the first and second pair of legs supplied on the under- 
* See preceding paper, ** On the Structure and Economy of Spiders,” 
side 
